A magnificent Marlon King 25-yard thunderbolt gave the Hornets a thoroughly deserved second-half lead following wave after wave of attacking pressure, but within minutes Paul Konchesky had broken through down the left and his cross towards the near post was neatly volleyed home by Bobby Zamora.
As with their opening day defeat at Everton, when they were the victims of a shocking penalty decision, Watford could again claim that luck was against them, because King had been unfortunate to see a first-half volley rebound away off the woodwork.
But even so there was still plenty to encourage the home fans ahead of this weekend's visit of Manchester United.
The home side set out their attacking stall from the opening whistle but it was West Ham who had the first decent opportunity when Chris Powell was caught in possession by Marlon Harewood, but some excellent covering defending by Jay DeMerit kept the striker at bay.
But the visitors' big first-half let-off came when Hameur Bouazza marauded away virtually the full-length of the pitch and his cross towards the near post was met by King, who tried to cleverly steer the ball wide of the Roy Carroll, only to see his attempt strike the upright.
Ashley Young was also close with an overhead kick that drifted just wide as Watford maintained their ascendancy up to, and after, the interval.
It took some smart defending from John Paintsil to prevent Bouazza connecting with a cross early in the second half, while at the other end Konchesky headed a reasonable opportunity straight at Ben Foster.
But the goal Watford so richly deserved arrived in sensational fashion 18 minutes into the second half when King spun away into space before hammering an unstoppable 25-yard drive past the helpless Carroll.
Yet the lead was to last just two minutes as Zamora scored his third goal of the season via the underside of the crossbar after Watford failed to deal with Konchesky's cross.
But West Ham could have had few complaints had Watford gone on to score a second which they so nearly did when, first, Danny Shittu narrowly headed a corner over, before Carroll's superb reflexes spared Anton Ferdinand's blushes after the England Under-21 defender had diverted a King cross towards his own net.
The Hornets' search for a winner continued late into the game with substitute Tamas Priskin narrowly failing to hook in a Shittu flick-on, before Damien Francis just failed to get on the end of a King cross, but the Hornets ultimately had to be content with a point.